Telephone-exchange trunking system.



F. LUBBERGER.

TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION FILED IUNE 10. 1909. RENEWED JUNE 15. 1918.

3 SHEETSSHEET I.

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Patented Jan. 28, 1919.

F. LUBBERGER.

TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION FILED JUNE 10, 1909. RENEWED JUNE 15, 1918.

Patented J an. 28, 1919,

3 SHEETSSHEET 2.

r F. LUBBERGER. TELEPHONE EXCHANGE TRUNKING SYSTEM. APPLICATION FILEDJUNE 10, 1909. RENEWED 'JUNE 1 51 I918.

Patented Jan 28, 1919.

3 SHEETS-SHEET 3 HI J UNITED STATES PATENT OFFICE. I

FRITZ LUBBERG-ER, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRICCOMPANY, OF CHICAGO, ILLINOIS, A. CORPORATION OF ILLINOIS.

TELEPHONE-EXCI-IANGE TRUNKING SYSTEM.

Specification of Letters Patent.

Patented Jan. 28, 1919.

Application filed June 10, 1909, Serial No. 501,259. Renewed June 15,1918. Serial No. 240,253.

To all whom it may concern Be it known that I, FRITZ LUBBERGER, asubject of the Emperor of Germany, and resident of Chicago, Cook county,Illinois, have invented a certain new and useful Improvement inTelephone-Exchange Trunking Systems, of which the following is aspecification.

My invention contemplates an improvement in telephone exchange systemswhereby the subscriber of one exchange may obtain trunking connection toanother exchange, and there obtain connection witlr the line of a localsubscriber, or obtain a trunking connection to a third exchange, for thepurpose of extending the call to the line of a called subscriberthereof. For example, in an automatic system employing selectors andconnectors I have found it desirable to provide means for trunkingbetween two common battery automatic exchanges, whereby a subscriber ofone may automatically call a subscriber of the other, and to providemeans whereby a subscriber of one of said automatic exchanges may callthrough the other automatic exchange to a third or local batteryautomatic exchange, thus obtaining connection with the line of asubscriber of the latter exchange. This means, of course, that thecommon battery subscriber may trunk automatically from the one commonbattery exchange to the other, and thus obtain connection with the lineof a common battery subscriber of the second exchange, or continue thecall through the second exchange to the third exchange, in the mannerstated. In trunking from the first common battery exchange to the secondcommon battery exchange for either purpose, the same trunking connectionmay be employedthat is to say, the trunking connection between the twocommon battery exchanges will be the same for calling a subscriber ofthe second exchange as it will for calling a subscriber of the thirdexchange. Thus the repeaters employed at the first exchange for giving acommon battery trunking connection between the two common batteryexchanges will be included in the trunking connection, regardless ofwhether the call is for a subscriber of the second or third exchange. Ifthe call be to the line of a subscriber of the second or common batteryexchange, then the repeater at the first exchange will receive currentfrom the common battery connector at the second exchange, as soon as thecalled subscriber removes his receiver, and the said repeater will thenfurnish talking current to the calling subscriber. The repeater at thesecond exchange is, however, of a difierent character, inasmuch as it isto be employed in trunking to the line of a local battery subscriber,and is not, therefore, equipped with means for furnishing current backover the circuit in the direction of the calling subscriber when thecalled subscriber answers. In other words, such a local battery repeateris preferably of a character to supply talking current to the line of acalling common battery subscriber as soon as the repeater is included inthe connectionthat is to say, as soon as the call extends to therepeater. Ordinarily a repeater for extending connection between acalling common battery subscriber and a called local battery subscriberis only required to furnish sufficient current for talking purposes. Inan arrangement such as described, however, where the call is to beextended through three exchanges, the second of which is a commonbattery exchange, the repeater at the second exchange must be of acharacter to supply enough current for operating the repeater at thefirst exchange, and for this purpose more current is required than forsimply enabling the calling subscriber to use his transmitter. In otherwords, the repeater at the second exchange must supply enough current tooperate a relay in the repeater at the first exchange, so that thisrelay may energize and thereby shift the battery at the first exchangeinto a bridge extending across the talking circuit, so that the callingsubscriber will receive talking current therefrom. In this way arepeater is used at the first exchange for calling a subscriber of thethird exchange, and this samerepeater is used in calling a subscriber ofthe second exchange. When the repeater at the first exchange is used forcalling a local battery subscriber at the third exchange, then thecalling subscriber receives talking current as soon as connection isobtained with the repeater at the second exchange; but when this samerepeater at the first exchange is used for calling a subscriber of thesecond exchange, then the calling subscriber receives talking current assoon as the called subscriber answer's. Hence the necessity forrepeaters at the second exchange which are of a character to supplysufficient current for operating the relays of the repeaters at thefirst exchange, and in a system characterized by my invention therepeaters at the second exchange are adapted for use in extendingconnection to the local battery subscribers of the third exchange, andare also adapted to supply sufficient operating current to the repeatersof the first exchange; and these repeaters of the first exchange areadapted for extending connection to the lines of common batterysubscribers, and are each adapted to supply talking current to thecalling subscriber when the called common battery subscriber answers.The nature of my invention will, however, hereinafter more fully appear.

In the accompanying drawings are represented diagrammatically thecentral or subexchange equipment employed by a sub or central exchangesubscriber in calling a subscriber of a local battery exchange throughan intervening common battery exchange, in a system embodying theprinciples of my invention, illustrating the operation and utility of myimproved repeater. V

Figure 1 represents a subscribers station A the line of whichterminatesat the central oflice in the line switch C; and at D is represented themaster switch controlling the group of line switches of which C is amember. At E is shown diagrammatically a first selector switch inconjunction with a repeater F embodying the principles of my invention.

Fig. 2 represents a selector H and a repeater M of the intermediatecommon battery central ofiice, with trunk conductors leading from therepeater to the selector H of Fig. 3.

In Fig. 3 is shown diagrammatically a selector switch H of a localbattery exchange and a connector switch I, and the selector isrepresented as connected with the trunk conductors leading to aconnector switch that operates and establishes connection with thenormal conductors of the line of substation A, which conductorsterminate in the line switch C;

These three exchanges maybe separated and some distance apart, and maybe connected by means of trunk lines which terminate in repeaters of myimproved type, or the common and local battery substations may beregarded as belonging to the same exchange. The repeaters F and M,nevertheless, are the connecting links between the three exchanges. Thesubstation A may be of any suitable or approved type. The one inconnection with which I have elected to illustrate my inventioncomprises a receiver 2, switch-hook 3 for controlling the substationcircuits, which controlling operations are accomplished through themedium of any suitable means, such as the cam arms 4, 5 and 6. As theswitch hook is lowered the cam 'arm' a momentarily presses the releasesprings 7 8 and 9 into engagement, whereby the substation lineconductors may be grounded simultaneously. When the switch hook is downthe cam arm 5 maintains a contact between the springs 10 and 11, therebybridging the ringer 12 in series with the condenser 13 across the line.The substation ground circuit is normally broken between the groundsprings 14 and 15 by the cam arm 6; but when said springs are together,then ground potential is provided from the battery to the ground post 16and to the release spring 7, as is usually the case in telephones ofthis type. The said substation. comprises the usual transmitter 17, andthe induction coil 18 having the primary winding 19 and secondarywinding 20.

Being an automatic substation it is provided with the usual vertical androtary impulse springs 21 and 22. Said substation is, of course,provided with a dial (not shown) which is secured to the shaft 23,together with the locking dog 24:. Furthermore, there is a locking cam25 that locks the dog 24 while the receiver is on the switch hook toprevent a rotation of the dial; For operating the impulse springs 21 and22 the substation is provided with an impulse wheel 26 that is securedto the shaft 23, which impulse wheel carries on its periphery theso-called vertical impulse teeth 27 and one rotary impulse toot-h 28.Furthermore, the rotary impulse spring 22 is of such construction thatwhen the dial is turned forward for the first digit the rotary impulsetooth 28 momentarily presses the said impulse spring onto the groundpost 16, whereby the rotary line conductor given a preliminary impulsefor operating the line switch C. The said impulse teeth are so arrangedthat when the dial is drawn down the impulse spring 21 is not carriedinto contact with the ground post 16; but as the dial returns, first thevertical teeth engage the vertical impulse spring 21, and after theyhave completed their work the rotary impulse tooth operates the rotaryimpulse spring In this operation the 'subscribers vertical lineconductor 29 is first'given a number of ground impulses, and then therotary line conductor 30 is given one ground impulse. It will be seenthat as long as the dial is out of normal position the dog 24 permitsthe primary circuit springs 31 and 32 to separate, thus preventing theimpulses that are delivered to either line conductor from passing to theother. The means whereby a subscriber may signal a called subscribercomprises the push button which, when pressechcarr'ies the spring 34 outof engagement with the contact point 35 and into engagement with thecontact point 36, whereby the vertical line conductor 29 is grounded.

The local battery substation A (Fig. 1) is similar to the substation A,the only dilference being in the arrangement to adapt one for commonbattery use and the other for local battery use. In the substation A thesprings 37 and 38 control the local circuit including the battery 39,transmitter 40 and primary winding 41. When the switch hook is down thecam arm 42 engages the spring 43, thereby bridging the ringer 44 inseries with the condenser 45 across the substation line conductors.Otherwise the substation A is the same as substation A in mechanicalconstruction and operation.

The line switch C is like the line switch disclosed in English PatentNo. 26,301 of 1906, and in the Western Electrician of Chicago, January25, 1908. The master switch D is similar in construction and operationto the master switches shown in the above publications.

The selector switches E, H and II are of the general type of selectorswitch disclosed in United States Patent No. 815,321, issued March 13,1906, to Keith, Erickson & Erickson. In this case, however, the usualbridgecut-ofi' relay and normal conductors are omitted.

The repeater F comprises the usual vertical and rotary line relays 46and 47 connected in series with the windings 48 and 49 of thedifferential relay 50. The relay 51 is bridged across the lineconductors 122 and 123, and is operated when battery current for talkingpurposes is thrown on said conductors from the connector I or therepeater M. The resistance 52 is connected to the trunk-release circuitto reduce the flow of current through the back-release relay of theselector when the release is initiated. By means of the condensers 53and 54 the trunk line is divided into two sections. On the left of thecondensers the im pulses are received by the line relays which operateto repeat the impulses to the conductors on the right of the condensers.My improved repeater M comprises the usual vertical and rotary linerelays 213 and 214 connected in series with the windings 215 and 216 ofthe differential relay 217. The slow-acting relay 226 acts as a polechanger for the rotary linethat is, normally, when the subscribers lineconductors are extended to the repeater M, the trunk lines between therepeaters F and M are supplied with talking battery current from groundG through the springs 218 and 219 of the slowacting relay 226 to thewinding 216 and relay 214, through the relay 51 of the repeater F,windings 213 and 215 to battery. When impulses are being sent by therepeater M the slow-acting relay 226 energizes and disconnects groundfrom the rotary line and connects battery therewith instead. The relayis made slow-acting in order that it may remain in an operated positionwhile the impulses are being delivered. By slow-acting is meant a relayso provided with a copper shield or other suitable arrangement that whenthe relay is once energized and the energizing circuit broken, the relaywill remain in its energized position for a moment. When the repeater isoperated to send impulses, the energizing circuit through the relay 226is broken for an instant only on each impulse, and hence the relayremains in its operated position; but after the impulses are deliveredthe relay returns to normal position, connecting the rotary line relayin series with the winding 216 to ground. The repeater M is equippedwith a resistance winding and two condensers for like purposes as in therepeater F.

The connector switch I is of the general type of connector switchdisclosed in United States Letters Patent No. 815,176, issued March 13,1906, to Keith, Erickson & Erickson, and is, as usual, connected to theringer generator J and the busy signaling machine K.

The selector switches E, H and H and the connector switch I, and thesubstation A are also shown and described in said English Patent No.26,301 of 1906.

In each of the drawings there is shown a battery 13 having its positiveterminal grounded at G. If the local battery section of automaticsubstations is in a central o'flice some distance from the commonbattery section, two batteries may be used; but if the two sections ofsubstations, local and common battery, are in the same exchangebuilding, or near by, one battery may be used.

A clearer understanding of my invention may be had from an explanationof its operation when employed by one subscriber to establish connectionwith another. Assume, for example, that the subscriber at substation Adesires to call the subscriber at substation A, the number of whichlatter is No.

To call this number the calling subscribed operates the dial in theusual manner for the first digit of the desired number. When the dial isturned forward for the first digit 2 the preliminary impulse tooth 28momentarily presses the rotary impulse spring 22 onto the ground post16, thereby closing an energizing circuit extending from the substationground G through the cooperat ing ground springs 14 and 15, ground post16, rotary impulse spring 22 to the rotary line conductor 30,bridge-cut-ofi springs 56 and 57, trip magnet 55, through the motormagnet relay springs 58 and 59, interrupter springs 60 and 61, andthrough the winding of the motor magnet 62 to the battery lead 63. Thetrip magnet 55 is energized over this circuit, but has a sufiicientlyhigh resistance to prevent enough current from flowing to operate themotor magnet 62. As soon as the trip magnet is energized its armature isattracted and the plunger thrust into an idle bank terminal. Nhen theplunger enters the bank terminal an energizing circuit is closed throughthe motor magnet relay 64 of the master switch.- The motor magnet 62 inturn energizes and operates to rotate the ratchet wheel 65,Vtherebyplacing the idle plungers opposite the next idle bank terminal. Thecircuit through the relay 6% extends from ground G through the winding66 to the common segment 67 of the master switch bank, throughthe wiper68 to the in dividual segment 69 which corresponds to the trunk terminaljust engaged), conductor 70, line switch bank springs 71 and 72, throughthe winding of the release magnet 73 to the battery lead 63, thencethrough battery B toground G. Although this circuitincludes the releasemagnet 73, the said magnet does not operatively energize, since therelay 64 is wound to a high resistance, While the winding of the releasemagnet 73 is of a comparatively low resistance. The re lay 64:, uponenergizing, operates to place th spring 59 in contact with thespring 7d,whereby the circuit is closed through the motor magnet 62, said circuitextending from ground G through the relay springs 74: and 59,interrupter springs and 61, through the winding of the motor magnet '62to the battery lead 63, thence through battery B to ground G. The motormagnet, upon energizing, attracts its armature 7 5, whereby the pawlupon the end of said armature 7 5 engages the ratchet wheel and rotatesthe latter one step. lVhen the armature 75 is attracted against themagnet cores 9 the interrupter springs 60 and 61 disengage, therebybreaking the energizing circuit of the motor magnet 62. The cam arm 7 6being in engagement with the pin 7 7 is operated to advance the plungershaft 78, and consequently all idle plungers that may be in normalposition, one step to another bank terminal. Also, the master switchbank wiper 68 is carried from the contact 69 (which corresponds to thetrunk line engaged) to another contact corresponding to the bankterminal before which the idle plungers are now resting. At the instantthat the plunger enters the bank terminal the bank springs are pressedinto contact as follows: 71 and 72, 79 and 80, 81 and 82 and 83 and 84.The engagement-of the springs 83 and 8 1 establishes a positive'guardingpotential which is transmitted by the private normal conductor 85 to theconnector private bank contact corresponding to the line of substationA. This potential protects the line of the calling subscriber from beingcalled by. another subscriber while theiprotected line is in use.

Also, when thesprings 83 and 84 engage, an energizing circuit isestablished through the bridge-cut-ofl' relay 86, said circuit extendingfrom ground G? through :the'bank springs 83 and 84, through thebridge-cut-ofmlay 86 to the battery lead 63 thence through bat-' tery Bto ground G. This relay, upon energizing, operates to break the contactbetween the springs 56, 57 and87 and to carry the spring 87 into contactFWltll the spring 88. The disengagement of the springs 56, 57 and 87disconnects the subscribers line conductors 29 and from the line switchtrip magnet 55. The guarding potential at the master switch bank forprotecting the trunk line conductors 89 and 90 from being seized byanother line switch extends from the battery lead 63, through therelease magnet 73 and bank springs 72 and 71, conductor 70' to theindividual contact 69. The closure of connection between the springs 79and 80 extends the subscribers vertical line conductor 29 to thetrunkline conductor 89. Ina similar manner the engagement of the banksprings 81 and 82 extends the subscribers rotary line conductor 30 tothe trunk line conductor 90. The trunk line conductors 89 and terminatein the-first selector switch E, and when the dial returns to normalposition for the first digit the vertical line relay is energized anumber of times, depending upon the digit called. The first digit calledbeing 2, the vertical impulse spring 21 is pressed onto the ground post16 twice, thereby closing an energizing circuit each time through thevertical line relay 91 of the first selector E. This circuit extendsfrom the substation groundG through the ground post and impulse spring21 to the vertical line conductor 29, bank springs 79 and 80, sideswitch iwiper 92, vertical line relay 91 to the battery lead 63,- thencethrough battery B to ground G." Each time that the vertical line relay91 energizes, the springs 93 and 94 are pressed into contact,therebyclosing a circuit through the vertical magnet 95 extending from ground Gthrough the springs 93 and 94-,-p'rivate magnet springs 96 and 97,vertical magnet 95 to the battery lead '63, thence through battery B toground G. The vertical magnet is thereby energized twice and the shaftand shaft wipers 98, 99 and 100 are raised one step at a timeuntilthe'shaft wipers are carried uptwo steps and brought opposite the banklevel in which are located the terminals of the trunk lines leading to aselector switch (F ig. 2). -Immediately following the lastverticalimpulse the rotary impulse spring 22 is pressed onto the groundpost 16, thereby energizing the rotary line relay 101 of the firstselector E. The rotary line relay energizes an'd pl-aces the springs 102and 93 in contact,whereby an energizing circuit is closed through theprivate magnet 103. Theprivate magnet, as

is well known, controls the side switch wipers 92, 104, 105 and 106. Theprivate magnet 103, upon energizing and denergizing, permits the sideswitch wipers to engage their respective contacts of the secondposition. hen the side switch wiper 105 engages the contact point 107 anenergizing circuit is closed through the rotary magnet 108 from ground Gthrough the side switch wiper 105, interrupter springs and windings ofthe rotary magnet 108 to the battery lead 63, thence through battery Bto ground G. The rotary magnet, upon energizing, operates to rotate theshaft wipers 98, 99 and 100 into engagement with the first bank contactof the second level. If the first contact is busy a. positive guardingpotential is present at the private bank contact, and as soon as thiscontact is engaged bythe shaft private wiper 100 an energizing circuitis established through the private magnet 103 from the grounded privatebank contact to the private wiper 100, through the back-release relay109, side switch wiper 106 (bearing in mind that the side switch isstill in second position), through the private magnet 103 to the batterylead 63, thence through battery B to ground G. This new energizingcircuit maintains the private magnet in an energized position, therebylocking the side switch in second position until the private wiper 100passes onto a contact upon which there is no guarding potential. Theback release relay 109 is not energized when included in the lockingcircuit of the private magnet 103 on account of the comparatively highresistance of said magnet. At the moment the energizing circuit throughthe private magnet is broken the said magnet deenergizes, permitting theside switch to pass to third position, whereby the energizing circuitthrough the rotary magnet is broken. Furthermore, when the side switchpasses to third position a guarding potential is established at theprivate bank contact corresponding'to the trunk line engaged. Thispotential extends from ground through the side switch wiper 106,back-release re lay 109 to the shaft wiper 100 which engages the privatebank contact. The subscribers line conductors '29 and 30 are thenextended to the conductors 110 and 111 leading to the repeater F. VVhenthe calling subscriber now operates his calling device for the seconddigit 2 the repeater F is operated to repeat the impulses .to the trunk.conductors 122 and 123 which lead to the selector H (Fig. 2). Theselector then responds to the impulses for the second digit, which arerepeated by the repeater F. When the vertical impulse spring 21 ispressed onto the ground post 16 on the return motion of the dial, anenergizing circuit is closed through the vertical line relay46, saidcircuit extending from the sub station ground G over the verticalconductors 29, 89 and 110, through the vertical relay 46, winding 48 tothe battery lead 63, thence through battery B to ground G. The verticalline relay 46 and the differential relay 50 energize, since thewinding48 alone carries current. The vertical line relay, upon energizing,presses the springs 124 and 125 into contact, thereby grounding thevertical trunk line conductor 122 from ground G through the springs 114and 115, 124 and 125, conductor 122, thence through the side switchwiper 194 and vertical line relay 195 to battery lead 128, thencethrough battery B to ground G. The vertical line relay opcrates to pressthe springs 196 and 197 into contact, which springs close a circuitthrough the vertical magnet 198 extending from ground .G through thesprings 196 and 197, private magnet springs 131" and 132 to the verticalmagnet 198, thence to battery lead 128, and through battery B to groundG. The vertical magnet operates to carry the shaft wipers 199, 200 and201 two steps to a point opposite the second bank level. Following thevertical impulses, the rotary impulse spring 22 is pressed onto theground post 16 and the rotary line re lay 47 of the repeater isenergized over a circuit extending from the substation ground G over therotary conductors 30, 90

and 111, through the rotary line relay 47 winding 49 of the differentialrelay 50, springs 113 and 121 to battery lead 63, thence through batteryB to ground G. The rotary line relay then operates to press the springs137 and 124 into contact, thereby repeating the rotary impulse to therotary trunk conductor 123 for energizing the ro tary line relay 202 ofthe selector H. This circuit extends from ground G through the springs114 and 115, 124 and 137, 119 and 120 to the rotary trunk conductor 123,through the side switch wiper 203 (Fig. 2), rotary line relay 202 to thebattery lead 128 thence through battery B to ground Gr. The rotary linerelay of the selector H then operates to press the springs 204 and 196into contact, thereby closing an energizing circuit for the privatemagnet 205 which, upon energizing and de'energizing, permits the sideswitch to pass from first to second position. When the side switch wiper206 en gages its second contact point an energizing circuit isestablished through the rotary magnet 207 from ground G through the sideswitch wiper 206, interrupter springs 208, through the winding of therotary magnet 207 to the battery lead 128, thence through battery B toground G. The rotary magnet operates in the manner explamed 1nconnection with the selector E to rotate the shaft wipers 199,200 and201 into engagement with bank contacts of an idle trunk line leading toa selector switch in the third exchange, assumed to be the selector H.When angidle contact is engaged the private magnet 205 trips the sideswltch to third position... The side switch wiper 209, upon engaging itsthird-position contact point, establishes a positive guarding potentialat the private bank contact of the trunk line engaged. This potentialextends from ground G to the side switch wiper 209 through thewinding-of the back-release relay 210, to the private wiper 201. .Vhenthe slde switch wipers 194 and 203 engage their respectivethird-position contact points, the subscribers line conductors 29 and-30 are extended to the trunk conductors 211 and .212 and to the repeaterM. An energizing circuitis immediately established through the linerelays 213 and 214 and the windings 215 and 216 of the double-woundrelay 217. This circuit extends from ground G through the springs 218and 219, through the winding 216 in series with the rotary line relay214 to the conductors 212 and 123, through the springs 235 and 236,-

through the relay '51 to the conductors 122 and 211, through thevertical line relay 213 in series with the winding 2:15 of the relay 217to the battery lead 220, thence through.

battery B to ground G. The relay 217, being wound diflerentially, doesnot operatively energize. The line relays 213 and 214 operate and pressthe springs which they control into contact. This operation is, however,without effect. When the relay 51 en ergizes it carries the spring 113out of con tact with the spring 121 and'into engagement with the spring237, separating, the spr gs 114 d 115, and the springs 119 and 120. Assoon as the spring 113 engages the spring 237 an energizing circuit'isestab lished, said circuit extending from ground G through the springs237 and 113, through the relay winding 49 of the differential re-- lay50, through the line relay 47 to conduc tor 111, thence throughsubstation A to conductor 110, through the line relay 46, wind mg 48 ofthe relay 50 to the battery lead 63, thence through battery B to groundG.

This circuit provides talking: battery current for that portion of theline to the left of the condensers 53 and 54, while the circuitpreviously traced through the relay 51' provides talking battery currentfor that portion of the line between the condensers 53 and 54 of therepeater F and condensers 238' and 239 of the repeater M, Now,.when thecalling subscriber operates his calling device for the third digit 2,the repeater M- is operated by impulses from the repeater F to operatethe line-relays of'the selector H (Fig. 3). The energizing circuit justtraced through the line and dififerential relays ofthe'repeater F isbroken at substatlon A when the subscriber turns his dial.

Atthe same time'th'e grounding of the verti'cal line. operates the linerelay 46 and the differential relay 50, since the windlng 48 alonecarries current. The operation of these relays have been hereinbefore described. The energizing of the relay 50 carries the spring 240 intocontact with the spring 241, and breaks the contact between the springs235 and .236. The separation of thelatter springs breaks the energizingcircuit through rthe relay 51, thus leaving the trunk lines leading tothe repeater M free to transmit impulses. The deenergizing' of the relay51 allows the spring 115 to agaln engage the spring 114, enabling theimpulse springs 125 and 137 to obtain ground when operated by the linerelays 46 and 47 When the line relays 46 and 47 energize, impulses aresent to the line relays'of the repeater M in the same manner that theywere formerly transmitted to the line relays of the selector H. When therelay 217 energizes, the springs 223, 224 and 225' are pressed intocontact, thereby energizing the slow-acting relay 226' from ground GThis relay, when energized, in turn separates the springs 218 and 219,227 and 228, and car riesthe springs 229 and 230, and 219 and 231, intocontact. The separation of the springs 227 and 228 disconnects thecondenser 239 from the trunk conductor 221,

thereby opening one side of the circuit through the repeater, theengagement of the springs 229 and230 connects the rotary im pulse springwith the conductor 222, and the shifting of the spring 219 shifts theconnection of the rotary relay 214 from the groundedto the non-groundedside of the battery. The relay 226,being slow-acting,-remains in itsenergized position until all the impulses are-delivered for the'thirddigit, after which it returnsto normal position, and the energizingcircuit is no longer maintained until the impulses are sent for the nextdigit. The vertical line relay, upon energizing, presses the springs 232and 233 into contact, thereby grounding the vertical trunk lineconductor 221 from ground G through the springs 225, 224 and'223,springs 232 and 233 to the conductor 221, thence through the side switchwiper 126 and vertical line relay 127 to the battery lead 128, thencethrough battery B to ground G. The.vertical line relay operates to pressthe springs 129 and 130 into contact, which closes a cirthereby closingan energizing circuit for the private magnet 141 which, upon energizingand deenergizing, permits the side switch to pass from first to secondposition. lVhen the side switch wiper 142 engages its second contactpoint an energizing circuit is established through the rotary magnet 143from ground G through the side switch wiper 142, interrupter springs144, through the windings of the rotary magnet 143 to the battery lead128, thence through battery B to ground G. The rotary magnet operates inthe manner explained in connection with the selector E to rotate theshaft wipers 134, 135, and 136 into engagement with bank contacts of anidle trunk line leading to the connector switch I. The side switch wiper145, upon engaging its third-position contact point, establishes apositive guarding potential at the private bank contact of the trunkline engaged. This potential extends from ground 11 to the side switchwiper 145, through the winding of the back-release re-' lay 146 to theprivate wiper 136. When the side switch wipers 126 and 139 engage theirrespective third-position contact points, the subscribers lineconductors 29 and 30 are extended to the trunk conductors 147 and 148,and to the connector switch I. The calling subscriber now operates thedial for the fourth digit 2, and in turn the repeaters F and M areoperated (in the manner previously explained) to repeat the impulses foroperating the vertical and rotary line relays 149 and 150 of theconnector. vVhen the vertical line relay 149 energizes, the relaysprings 151 and 152 are pressed into contact, thereby closing thecircuit through the vertical magnet 153, said circuit extending fromground G through the springs 151 and 152, private magnet springs 154 and155, side switch wiper 156, vertical magnet 153 to the battery lead 128,thence through battery 13 to ground G. The vertical magnet operates andcarries the shaft wipers 157, 158 and 159 two steps in a verticaldirection, opposite the bank level in which are located the terminals ofthe line No 22220. Following the vertical impulses the rotary line relayenergizes to place the springs 160 and 151 in contact to close a circuitthrough the private magnet 161, which latter operates to place the sideswitch wipers in second position. When the side switch wiper 156 engagesits second-position contact point the rotary magnet 162 is placed underthe control of the vertical line relay, so that when the dial isoperated for the last digit 0, and the vertical relay 149 presses thesprings 151 and 152 into contact ten times, then an energizing circuitis closed through the rotary magnet 162 ten times, instead of throughthe vertical magnet 153. The rotary magnet operates, in response to theop eration of the dial for the last digit, to carry the shaft wipers157, 158 and 159 into engagement with the tenth contact of the secondlevel of the connector bank. Following the vertical impulses for thedigit 0, the usual rotary impulse energizes the rotary line relay 150,and again the private net 161 is energized to permit the side switchwipers 156, 163, 164 and 165 to pass to third position. The engagementof the third-position contact point by the side switch wiper 156 placesthe vertical line relay 149 in control of the ringer relay 166 in thesame manner in which the rotary magnet 162 came under the control of thevertical line relay when the wiper 156 passed from first to secondposition. WVhen the side switch wiper 165 passes to third position apositive guarding potential is established at the private bank contactof the called line. Also, this guarding potential provides an energizingcircuit for the bridge-cutoff relay 167 of the line switch C of thecalled line. This energizing circuit extends from ground G through theside switch wiper 165 to the shaft wiper 159, thence over the normalconductor 168, through the winding of the 'bridge-cut-off relay 167 tothe battery lead 128, thence through battery B to ground G. This relay,upon. energizing, operates to sep arate the springs 169, 170 and 171 andto carry the springs 169 and 172 into contact. The side switch wipers163 and 164, upon passing to third position, extend the callingsubscribers line conductors 29 and 30 to the normal conductors 173 and174 of the called line. The calling subscriber at substation A,therefore, presses the signaling button 33, whereby an energizingcircuit is established through the vertical line relay 149 of theconnector. The connector line relay operates to close a circuit throughthe ringer relay 166, said circuit extending from ground G through thesprings 151 and 152, private magnet springs 154 and 155, side switchwiper 156, through the -winding of the ringer relay 166 to the batterylead 128, thence through battery B to ground G. The ringer relay, uponenergizing, operates to separate the calling and called lines and tobridge across the latter the terminals of the ringer generator J.thereby transmitting signaling current to the ringer 44 of the calledsubstation No. 22220. The path of the ringing current extends from thegenerator J through the ringer springs 17 5 and 176, side switch wiper163, shaft wiper 157 to the normal conductor 173, bridge-cut-ofi springs172 and 169 to the line conductor 177, to the switch hook 42 and spring43, through the ringer 44, condenser 45 to the rotary line conductor178, normal conductor 174, shaft wiper 158, side switch wiper 164,ringer relay springs 179 and 180 back to the generator J. In response tothe signal the subscriber at substation No. 22220 removes the receiverfrom the switch hook. The substation A receives talking battery currentfrom the local battery 39. The two arenow connected and communicationmay be carried on over the circuit shown by the heavy line conductors inFigs. 1, 2 and 3.

The release of the central oiiice switching apparatus is brought aboutwhen the call ing subscriber restores his receiver to the switch hook,thereby momentarily pressing the release springs 7, 8 and 9 intocontact, which grounds both line conductors 29 and 30 simultaneously.Grounding the rotary line conductor 30 places a short-circuit upon therotary line relay 47 and the relay winding 49, said circuit extendingfrom ground G through the springs 7 8 and 9 to the rotary line conductor30, trunk conductors 90 and 111, through the line relay 47 and thewinding 49, and springs 113 and 237 to ground G The relay 50 then.operatively energizes and separates the springs, and 236 and closes thesprings 240 and 241, since the winding 48 alone carries current. Theseparation of springs 235 and 236 removes the energizing circuit throughthe relay 51 and thereby removes the shortcircuit upon the line relayand winding 49. The relay 51, deenergizing, allows the spring 113 toreturn into contact with the spring 121, thus restoring main battery(the nongrounded pole) to one side of the winding 49, and completing anenergizing circuit through this winding and the relay 47 to ground G.The springs 114 and 115 like wise make contact and restore ground to thespring 124. Since the line relays 46 and 47 are now energized, ground isthrown on both sides of the line conductors 122'and 123 from ground Gthrough the spring 125 on the vertical side, and the spring 137 on therotary side. Grounding the rotary line conductor 123v places ashort-circuit upon the rotary line relay 214 and the relay. winding 216,said-*circuit extending from ground G through the springs 114 and 115,124 and 137, 119 and 120, rotary line conductor 123, trunk conductor212, through the line relay 214 and winding 216, springs 219 and 218 toground G. The relay 217 then operatively energizes and places thesprings 223, 224 and 225 into contact, since the winding 215 alonecarries current. The engagement of the above springs closes anenergizing circuit through the slow-acting relay 226, as previouslystated. This relay now operates to shift the spring 219 from the spring218 and into contact with the spring 231, whereby the rotary line relay214 in series with the winding 216 is disconnected from the groundconnection G and placed in contact with the battery lead 220, therebyremoving the short-circuit and establishing an energizingclrcultinstead- The vertical and rotary line relays 213 and 214 energizesimultaneously and press the springs they control into contact. Thisgrounds the trunk line conductors 221 and 222 simultaneously andenergizes the vertical and rotary line relays 149 and 150 oftheconnector. The line relays of the connector, upon energizingsimultaneously, place the trunk-release springs 181 and 182 in contact,which closes an energizing circuit through the connector release magnet183 in series with the release relay 146 of the selector H. This circuitextends from ground G through the side switch wiper 145, winding of theback-release relay 146 to the shaft wiper 136,-then to the trunk-releasesprings 181 and 182, through the release magnet 183 to the battery lead128, thence through battery B to ground G. The release magnet 183, uponenergizing, operates to restore the switch shaft and side switch tonormal position. The release relay 146, upon energizing, operates toclose the springs 184 and 185 in contact, which establishes anenergizing circuit from ground G through the release magnet 1860f theselector. The engagement of the trunk-release springs 242 and of therepeater, upon thesimultaneous energizing of the line relays, closes anenergizing circuit through the release relay 210 of the first selector.This circuit eX tends from ground G through the side switch wiper 209and back-release; relay 210. to the shaft wiper 201, through thetrunkmelease springs 242 and 243, resistance winding 244, sprin s 219and 231 to the battery lead 220, thence through battery B to ground 7 G;The backsrelease relay thereupon energizes and places the springs 245and 246 into engagement, and closes an energizing circuit for therelease magnet 247. The engagement of the trunk-release springs 187 and,188 of the repeater F, upon the simultaneous energizing of the linerelays, closes an energizing circuit through the release relay 109 ofthe first selector. This circuit extends from ground G through the sideswitch wiper 106 and back-release relay to the shaft wiper 100, throughthe trunk-release springs 187 and 188, resistance winding 52, springs240 and 241 to the battery lead 63, thence through battery B to groundG. The back-release relay thereupon ener gizes and places the springs189 and 190 in engagement, and closes an energizing circuit for therelease magnet 191; and the release magnet in turn, upon energizing,operates to close the springs 192 and 193 in contact, thereby closingthe circuit through the release magnet 7 3 of the line switch C. All. ofthe release relays and the magnet thus energizedattr'act theirrespective armatures and remain in readiness to release their respectiveswitches when the ground connection to the line conductors 29 and 30 isremoved by the disengagement of the release springs 7, 8 and 9.

From the foregoing it will be seen that the repeater not only repeatsimpulses originating in atelephone of the common battery section, tooperate the switches of the local battery section, but also that, afterthe connection is established, the repeater enables the callingsubstation to receive talking battery current from the main centralbattery. The repeaters M and F form a simple and efficient means forenabling a subscriber of a common battery automatic exchange to call andcommunicate with a subscriber of a local battery automatic exchange.

From the foregoing it will be seen that 1 provide an arrangement wherebya subscriber of one exchange may automatically trunk from one exchangeto the other for either one of two purposes. First, for the purpose ofobtaining connection with the line of a ommon battery subscriber at thesecond exchange, and, second, for the purpose of obtaining connectionwith a repeater at the second exchange, whereby the call may be extendedto the line of a local battery subscriber at the third exchange. Therepeaters at the second exchange are adapted for extending connection tolocal battery subscribers, and are also, as explained, adapted forsupplying suiiicient current in the other direction to operate thepole-changing relays of the repeaters at the first exchange. For thispurpose more current is required than would be necessary in a case wherethe current obtained through the repeater M is necessary simply forenabling the calling subscriber to use his transmitter. In other words,the current sent back over the line circuit from the repeater M must bestronger when it is to be employed for operating the relay 51 than wouldbe the case were the said current to be used simply for operating thetransmitter 17 at the calling substation. Hence, the relay 51 receivesall of such current, and during conversation there is nothing inmultiple with this relaythat is to say, there isnothing in bridge of thecircuit between it and the battery B of Fig. 2. It is desirable that therepeater F be suitable for extending connection to a common batterysubscriber, and such being the case it must be capable of respondingwhen the called common battery subscriber answers, so as to supplytalking current to the calling line in the usual and well-known manner.Suppose, for example, that subscriber A desires to call a common batterysubscriber of the second exchange, as indicated in Fig. 2. In such casethe repeater F will be used in extending connection through the selectorH to the common battery connector shown in Fig. 2, which connector willthen seize the line of the called common battery subscriber. It will beunderstood that certain levels of the selectors H may have access torepeaters M, and certain other levels may have access to common batteryconnectors. The common battery connector in Fig. 2 is shown onlydiagrammatically to illustrate the talking circuit through it and thecircuits over which talking battery current is furnished to the callingand called lines. The opera tions of the common battery connector bymeans of which it finds the called line are substantially the same asthose of the connector I. WVhen the called subscriber answers, a batteryis bridged across the talking circuit by the relay 260 in the connectorby shifting the connection of the rotary line relay 261 from thenon-grounded to the grounded terminal of the battery, and cur rent fromthis battery then energizes the relay 51, which relay in turn bridgesanother battery across the circuit to supply talking current to thecalling subscriber. Thus the repeater F is capable of responding toeither a common battery connector or another repeater for the purpose ofestablishing a flow of talking current in the calling line. It isbecause this repeater F is desirably of a character to extend connectionto a called common battery subscriber that the necessity arises for arepeater M of a character to extend connection to a local batterysubscribers line, and furnish current back over the circuit to the firstexchange. The relay 51 of the repeater F must be energized in order tosupply current to the calling subscriber. lVhen connection is made to acommon battery subscriber the common battery connector completes thecircuit for the relay 51. A local battery connector, however, does notsupply current to the trunk leading to it, but current for energizingthe relay 51 is supplied from the repeater M. In a repeater required todo the work of the repeater F both sides of the circuit are preferablynormally connected with the same side of the battery; but in a repeaterrequired to do the work of the repeater M the battery is normally inbridge of the circuit. The repeaters M are, therefore, adapted for usein extending connec tion to a local battery subscriber, in a sys tememploying repeaters F that are adapted for use in extending connectionto common battery subscribers. The repeaters M are, therefore, in thenature of means for enabling the common battery subscribers to use therepeaters F for extending connection to local battery subscribers.

It will be seen that my invention relates more especially to that typeof automatic system in which the subscribers are divided into groups andin which connectors are provided having vertical motion to selectgroups, and then rotary motion to find the called subscriber in anyselected group. As shown, each group is composed of ten subscribers,there being ten of these groups for each connector-that is to say,'thereare ten levels in each connector and in each level there are theterminals of ten subscribers lines. It will be understood, of course,that the subscribers lines are provided with multiple terminals, so thateach subscriber is represented in several connectors. The selectors alsohave vertical motion to select groups or divisions of the exchange, andthen rotary motion to find an idle trunk line in any selected group.

What I claim as my invention is 1. In a telephone system, commonbatterysubscribers lines, local battery subscribers lines, a repeater includingrelays, and means whereby said repeater is operative for extendingconnection to either a common battery or a local battery subscribersline.

2. In a telephone system, common battery subscribers lines, localbattery subscribers lines, a repeater including relays at the commonbattery exchange operative for extending connection to a common batterysubscribers line, and means at another exchange whereby the saidrepeater is also operative for extending connection to a local batterysubscribers line.

3. In a telephone system, common battery subscribers lines, localbattery subscribers lines, means including a repeater for extendingconnection from one common battery line to another, adapted to establishtalking current in the calling line when the called subscriber answers,and means whereby said repeater is also operative for extendingconnection to a local battery subscribers line, adapted to cause therepeater to establish a flow of talking current in the calling linebefore the called subscriber answers.

4. In a telephone system, common battery subscribers lines, localbattery subscribers lines, a repeater for use in extending connectionfrom one common battery line to another, and another repeater forenabling a calling common battery subscriber to use said firstmentionedrepeater in extending a call to a local battery subscribers line.

5. In a telephone system, a first exchange, a second exchange, a thirdexchange, repeaters at the first exchange for enabling the subscribersthereof to call subscribers of the second exchange, and means at thesecond exchange for enabling the subscribers of the first exchange touse said repeaters in calling subscribers of the third exchange.

6. In a telephone system, a first common battery exchange, a secondcommon battery exchange, a local battery exchange, repeaters at thefirst exchange for enabling the subscribers thereof to call subscribersof the second exchange, and repeaters at the second exchange forenabling the subscribers of the first exchange to use saidfirst-mentioned repeaters in calling subscribers of the local batteryexchange.

7 A telephone exchange system, a line circuit, a repeater connectedthereto and having one side of the line circuit normally grounded, abattery normally in bridge of the line circuit, and a relay for shiftingone side of the line circuit to the other pole of the battery,preliminary to the use of the repeater for transmitting impulses.

8. A telephone exchange system repeater having a battery bridge normallyacross the talking circuit'thereof, a relay for shifting one side of thecircuit to the other pole of the battery, and a double-wound relaycontrolling said first-mentioned relay.

9. A telephone exchange system repeater having an impulse spring, atrunk conductor normally disconnected therefrom, and a relay for closingand holding closed the connection between said trunk conductor and saidspring while the series of impulses are being transmitted by therepeater, said relay denergized during talking.

10. A telephone exchange system, trunk conductors, a repeater having thetrunk conductors transposed therein, a condenser in each of saidconductors, and a relay for disconnecting one of said condensers from apart of one of said conductors during transmission of impulses over thatpart of said conductor.

11. A telephone exchange system, trunk conductors, a repeater havingsaid conductors transposed therein, a condenser in each of saidconductors, and a relay for disconnecting one of said condensers from apart of its conductor during transmission of impulses over that part ofsaid conductor, said relay deenergized during talking.

12. A telephone exchange system repeater having an impulse spring, atrunk conductor normally disconnected therefrom, another trunkconductor, a line relay and a differential relay, a relay adapted toconnect the impulse spring to its trunk conductor and open the otherconductor, and adapted also to place said line relay and differentialrelay in condition to be energized responsive to the calling subscriber.

13. In a telephone system, a trunk circuit including two trunkconductors, a condenser, an impulse spring, and a relay operative bydenerg'izing to connect one trunk conductor with the condenser anddisconnect the other conductor from said spring, and to connect one sideof the trunk circuit to ground.

14. In a telephone system, a repeater for use in extending connectionfrom a calling common battery subscriber to a called local batterysubscriber, a battery therefor, another repeater, and circuitconnections whereby current is supplied from the battery through thefirst repeater to the other repeater during talking, said first repeaterbeing free from local circuits during talking.

15. In an automatic telephone exchange system in which the subscribersare divided into groups, common battery subscribers lines, local batterysubscribers lines, a repeater, and electrically controlled means wherebysaid repeater is operative for extending connection to either a commonbattery or a local battery subscribers line, said means having verticalmotion to select groups and rotary motion to find the called subscriberin any selected group.

16. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, common battery subscriberslines, local battery subscribers lines, a repeater including relays, andelectrically controlled means whereby said repeater is operative forextending connection to either a common battery or a local batterysubscribers line, said means having vertical motion to select groups androtary motion to find an idle trunk in any selected group.

17. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, common battery subscriberslines, local battery subscribers lines, a repeater including relays atthe common battery exchange operative for extending connection to acommon battery subscribers line, and switches at another exchangecontrolled by said repeater whereby the said repeater is also operativefor extending connection to a local battery subscribers line, saidswitches having vertical motion to select groups and rotary motion tofind an idle trunk in any selected group.

18. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, common battery subscriberslines, local battery subscribers 'lines, means including a repeater forextending connection from one common battery line to another, adapted toestablish talklng current in the calling line when the calledsubscriberanswers, and electrically controlled means whereby said repeater is alsooperative for controlling a connection to a local battery subscrlbersline, adapted to cause the repeater to establish a flow of talkingcurrent in the calling line before the called subscriber answers, saidmeans having vertical motion to select groups and rotary motion to findan idle trunk in any selected group;

19. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, common battery subscriberslines, local battery subscribers lines, a repeater for use in extendingconnection from one common battery line to another, and another repeaterfor enabling a calling common battery subscriber to use saidfirst-mentioned repeater in extending a call to a local batterysubscribers line, said system provided with automatic means controlledby the repeaters having vertical motion to select groups and rotarymotion to find an idle trunk in any selected group.

20. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a first exchange, a secondexchange, a third exchange, repeaters at the first exchange for enablingthe sub scribers thereof to call subscribers of the second exchange, andelectrically controlled means at the second exchange for enabling thesubscribers of the first exchange to use said repeaters in callingsubscribers .of the third exchange, said system provided with automaticmeans controlled by the repeaters having vertical motion to selectgroups and rotary motion to find an idle trunk in any selected group.

21. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a first common battery exchange,a second common battery exchange, a local battery exchange, repeaters atthe first exchange for enabling the subscribers thereof to callsubscribers of the second exchange, and repeaters at the second exchangefor enabling the subscribers of the first exchange to use saidfirst-mentioned repeaters in calling subscribers of the local batteryexchange, said system provided with means controlled by the repeatershaving vertical motion to select groups and rotary motion to find anidle trunk in any selected group.

22. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a line circuit therefor, arepeater connected thereto and having one side of the line circuitnormally grounded, a battery normally in bridge of the line circuit, anda relay for shifting one side of the line circuit to the other pole ofthe battery, preliminary to the use of the repeater for transmittingimpulses, said system provided with automatic means controlled by therepeater having vertical motion to select groups and rotary motion tofind an idle trunk in any selected group.

23. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a-repeater therefor having abattery bridge normally across the talking circuit thereof, a relay forshifting one side of the circuit to the other pole of the battery, and adouble-wound relay controlling said first-mentioned relay, said systemprovided with automatic means con trolled by the repeater havingvertical motion to select groups and rotary motion to find an idle trunkin any selected group.

24. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a repeater therefor having animpulse spring, a trunk conductor normally disconnected therefrom, and arelay for closing and holding closed the connection between said trunkconductor and said spring while the series of impulses are beingtransmitted by the repeater, said relay deenergized during talking, saidsystem provided with automatic means controlled by the repeater havingvertical motion to select groups and rotary motion to find an idle trunkin any selected group.

25. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, trunk conductors, a repeaterhaving the trunk conductors transposed therein, a condenser in each ofsaid conductors, and a relay for disconnecting one of said condensersfrom a part of one of said conductors during transmission of impulsesover that part of said conductor, said system provided with automaticmeans controlled by the repeater having vertical motion to select groupsand rotary motion to find an idle trunk in any selected group.

26. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, trunk conductors, a repeaterhaving said conductors transposed therein, a condenser in each of saidconductors, and a relay for disconnecting one of said condensers from apart of its conductor during transmission of impulses over that part ofsaid conductor, said relay de'energized during talking, said systemprovided with automatic means controlled by the repeater having verticalmotion to select groups and rotary motion to find an idle trunk in anyselected group.

27. In an automatic telephone exchange trunking system in which thetrunks thereof are divided into groups, a repeater therefor havinganimpulse spring, a trunk conductor normally disconnected therefrom,another trunk conductor, a line relay and a differential relay, a relayadapted to connect the impulse spring to its trunk conductor and openthe other conductor, and adapted also to place said line relay anddifferential relay in condition to be energized responsive to thecalling subscriber, said system provided with automatic means controlledby the repeater having vertical motion to select groups and rotarymotion to find an idle trunk in any selected group.

28. In an automatic telephone exchange Copies of this patent may beobtained for trunking system in which the trunks thereof are dividedinto groups, a repeater therefor for use in extending connection from acalling common battery subscriber to a called local battery subscriber,a battery therefor, another repeater, and circuit connections wherebycurrent is supplied from the battery through the first repeater to theother repeater during talking, said first repeater being free from localcircuitsduring talking, said system provided withautomatic meanscontrolled by the repeater having vertical motion to select groups androtary motion to find an idle trunk in any selected group.

29. In a telephone system, common battery subscribers lines, localbattery subscribers lines, a repeater including relays, and electricallycontrolled means whereby said repeater is operative for extendingconnection to either a common battery or a local battery subscribersline.

30. In a telephone system, common battery subscribers lines, localbattery subscribers lines, a repeater including relays at the commonbattery exchange operative for extending connection to a common batterysubscribers line, and electrically controlled means at another exchangewhereby the said repeater is also operative for extending connection toa local battery subsc-ribers line.

31. In a telephone system, common battery subscribers lines,l0cal-battery subscribers lines, means including a repeater forextending connection from one common battery line to another, adapted toestablish talking current in the calling line when the called subscriberanswers, and electrically controlled means whereby said repeater is alsooperative for extending connection to a local battery subscribers line,adapted to cause the repeater to establish a flow of talking current inthe calling line before the called subscriber answers.

32. In a telephone system, a first exchange, a second exchange, a thirdexchange, repeaters at the first exchange for enabling the subscribersthereof to call subscribers of the second exchange, and electricallycontrolled means at the second exchange for nabling the subscribers ofthe first exchange to use said repeaters in calling subscribers of thethird exchange.

Signed by me at Chicago, Cook county, Illinois, this third day of June,1909.

FRITZ LUBBERGE-R. Witnesses:

EDWARD D. FAL'ES, ARTHUR J. RAY.

five cents each, by addressing the Commissioner of Patents,

Washington, D. G.

